Nature and origin of a Pleistocene-age massive ground-ice body exposed in the Chapman Lake moraine Complex, central Yukon Territory, Canada

Abstract A massive ground-ice body was found exposed in the headwall of a thaw flow developed within the Chapman Lake terminal moraine complex on the Blackstone Plateau (Ogilvie Mountains, central Yukon Territory), which is contemporaneous to the Reid glaciation. Based on visible cryostructures in t...

Full description

Bibliographic Details
Published in:Quaternary Research
Main Authors: Lacelle, Denis, Lauriol, Bernard, Clark, Ian D., Cardyn, Raphaelle, Zdanowicz, Christian
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press (CUP) 2007
Subjects:
Ice
Online Access:http://dx.doi.org/10.1016/j.yqres.2007.05.002
http://api.elsevier.com/content/article/PII:S0033589407000683?httpAccept=text/xml
http://api.elsevier.com/content/article/PII:S0033589407000683?httpAccept=text/plain
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400014186
Description
Summary:Abstract A massive ground-ice body was found exposed in the headwall of a thaw flow developed within the Chapman Lake terminal moraine complex on the Blackstone Plateau (Ogilvie Mountains, central Yukon Territory), which is contemporaneous to the Reid glaciation. Based on visible cryostructures in the 4-m-high headwall, two units were identified: massive ground ice, overlain sharply by 2 m of icy diamicton. The nature and origin of the Chapman Lake massive ground ice was determined using cryostratigraphy, petrography, stable O–H isotopes and the molar concentration of occluded gases (CO 2 , O 2 , N 2 and Ar) entrapped in the ice, a new technique in the field of periglacial geomorphology that allows to distinguish between glacial and non-glacial intrasedimental ice. Collectively, the results indicate that the Chapman Lake massive ground ice formed by firn densification with limited melting–refreezing and underwent deformation near its margin. Given that the massive ground-ice body consists of relict glacier ice, it suggests that permafrost persisted, at least locally, on plateau areas in the central Yukon Territory since the middle Pleistocene. In addition, the d value of Chapman Lake relict glacier ice suggests that the ice covering the area during the Reid glaciation originated from a local alpine glaciation in the Ogilvie Mountains.